452 GEOLOGY OF OHIO. 



of the country may have ch<inged so that the land is readily drained at 

 present, and this still be the true explanation of these black lands in 

 this and adjoining counties. Moisture made rank and abundant vege- 

 tation, while it also impeded its entire decay. The partially decayed 

 vegetable products accumulated, and mingling with the clay below, 

 formed that rich, dark-brown loam. But there is unfortunately a larger 

 area of thin and light-colored soil in the county than of the soil just 

 described. This thin soil is not peculiar to this county, but is found in 

 other counties situated in like manner. Its color shows it to be quite 

 destitute of the products of vegetation. It dififers equally from the yel- 

 low clay soils of the uplands of Butler, Warren, and Hamilton counties, 

 and seems less capable of being made productive. The clay of this 

 class of soils is impermeable to water, and is so situated that water has 

 drained off readily, and has not stood upon it in natural swamps. The 

 soil is composed of a fine-grained material and is compact, and sheds 

 water like a roof. How the circumstances in which the fine-grained ma- 

 terial was deposited differed from those in which other drift deposits were 

 made, I will not undertake to state. This soil seems to have been ex- 

 hausted rather than enriched by ages of primeval vegetation. What 

 chemical analysis would show it to lack of fertilizing material, I cannot 

 say, but the deficiency of limestone pebbles in it would indicate that it 

 might be lacking in lime, and it has not had the advantage of being 

 overspread with decaying bowlders, which add to a soil potash and other 

 fertilizing ingredients. It seems to have been the least fine sediment 

 deposited from receding water — lifeless water. 



This soil, lying so as to drain away water, and not of a nature to ab- 

 sorb and retain it, became covered slowly with vegetation. But it al- 

 ways lacked that rankness and exuberance of vegetation which lower 

 and moister places possessed. Still many, countless, generations of plants 

 and unknown crops of trees have grown and decayed here without leav- 

 ing behind them much vegetable matter commingled with the soil. 

 What has become of the substance of plants that it has not accumulated in 

 the soil 1 The answer must be that the growth upon this soil have passed 

 back to their original elements — have gone as they came — in the form of 

 water and gases. The bulk of vegetation is coiuposed of water (oxygen 

 and hydrogen), carbonic acid (carbon and oxygen), and nitrogen. When 

 vegetation decays these materials are evolved, and pass off into the at- 

 mosphere. It is when decay is impeded that vegetable matter accumu- 

 lates in the soil. Mould is partially decayed vegetation. When vegeta- 

 ble products are protected from the atmosphere by water their decay is 

 retarded and impeded, and certain compounds are formed of a complex 



